Boiler Heat Exchanger

ABSTRACT

A coil assembly for a combustion chamber includes a first tube arranged into a plurality of inner coils and a second tube arranged into a plurality of outer coils that surround the plurality of inner coils. Each inner coil contacts adjacent inner coils. The plurality of outer coils are separated from adjacent outer coils by a plurality of spaces. The first and second tubes are configured to transport a heat transfer fluid (HTF). The plurality of inner coils are separated from the plurality of outer coils by a gap. The coil assembly also includes a cylindrical shroud surrounding at least a portion of the coil assembly. The cylindrical shroud has a length that is less than a length of the coil assembly.

TECHNICAL FIELD

This invention relates generally to boilers and more particularly to a heat exchanger for a boiler.

BACKGROUND OF THE INVENTION

Hydronic heating is used by various heating appliances. For example, residences and commercial buildings may utilize heat exchangers that circulate heat transfer fluid (“HTF”) such as water to provide heated air to living spaces. As another example, HTF may be used for ground thawing, concrete curing, snow melting, and slab heating. Typically, boilers are used to heat the HTF that is used in these and other applications. Many existing boilers, however, are inefficient and wasteful.

SUMMARY OF THE INVENTION

According to embodiments of the present disclosure, disadvantages and problems associated with previous boilers may be reduced or eliminated.

In some embodiments, a coil assembly for a combustion chamber includes a first tube arranged into a plurality of inner coils and a second tube arranged into a plurality of outer coils that surround the plurality of inner coils. Each inner coil contacts adjacent inner coils. The plurality of outer coils are separated from adjacent outer coils by a plurality of spaces. The first and second tubes are configured to transport a heat transfer fluid (HTF). The plurality of inner coils are separated from the plurality of outer coils by a gap. The coil assembly also includes a cylindrical shroud surrounding at least a portion of the coil assembly. The cylindrical shroud has a length that is less than a length of the coil assembly.

Certain embodiments of the present disclosure may provide one or more technical advantages. For example, certain embodiments provide a central combustion chamber/heat exchanger that includes uniquely arranged helically coils and an exterior shroud. The arrangement of the helical coils and the shroud of certain embodiments causes turbulent contact between hot flue gases and the coils, thereby increasing heat exchange efficiency over existing systems. In some embodiments, two layers of helically-looped water tubes in the combustion chamber cause hot flue gasses to make two passes of turbulent flow over the coil tube surfaces before exiting the chamber, further increasing the heat exchange efficiency.

Certain embodiments of the present disclosure may include some, all, or none of the above advantages. One or more other technical advantages may be readily apparent to those skilled in the art from the figures, descriptions, and claims included herein.

BRIEF DESCRIPTION OF THE DRAWINGS

To provide a more complete understanding of the present invention and the features and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a hydronic heater, according to certain embodiments;

FIG. 2 illustrates a combustion chamber assembly of the hydronic heater of FIG. 1, according to certain embodiments;

FIG. 3 illustrates a cut-away view of the combustion chamber assembly of FIG. 2, according to certain embodiments;

FIGS. 4A-4C illustrate various views of a refractory flue gas roller of the combustion chamber assembly of FIG. 2, according to certain embodiments;

FIGS. 5A-5B illustrate various views of a coil assembly of the combustion chamber assembly of FIG. 2, according to certain embodiments;

FIG. 6 illustrates an inner coil assembly of the coil assembly of FIG. 5A, according to certain embodiments; and

FIG. 7 illustrates an outer coil assembly of the coil assembly of FIG. 5A, according to certain embodiments.

DETAILED DESCRIPTION OF THE DRAWINGS

hydronic heating is used by various heating appliances. For example, residences and commercial buildings may utilize heat exchangers that circulate heat transfer fluid (“HTF”) such as water to provide heated air to living spaces. As another example, HTF may be used for ground thawing, concrete curing, snow melting, and slab heating. Typically, boilers are used to heat the HTF that is used in these and other applications. Many existing boilers, however, are inefficient and wasteful.

To address the problems and inefficiencies of existing systems, the disclosed embodiments provide a central combustion chamber/heat exchanger that includes uniquely arranged helically coils and an exterior shroud. The arrangement of the helical coils and the shroud of certain embodiments causes turbulent contact between hot flue gases and the coils, thereby increasing heat exchange efficiency over existing systems. In some embodiments, two layers of helically-looped water tubes in the combustion chamber cause hot flue gasses to make two passes of turbulent flow over the coil tube surfaces before exiting the chamber, further increasing the heat exchange efficiency.

The advantages and features of certain embodiments are discussed in more detail below in reference to FIGS. 1-7. FIG. 1 illustrates a hydronic heater; FIG. 2 illustrates a combustion chamber assembly of the hydronic heater of FIG. 1; FIG. 3 illustrates a cut-away view of the combustion chamber assembly of FIG. 2; FIGS. 4A-4C illustrate various views of a refractory flue gas roller of the combustion chamber assembly of FIG. 2; FIGS. 5A-5B illustrate various views of a coil assembly of the combustion chamber assembly of FIG. 2; FIG. 6 illustrates an inner coil assembly of the coil assembly of FIG. 5A; and FIG. 7 illustrates an outer coil assembly of the coil assembly of FIG. 5A, according to certain embodiments.

FIG. 1 illustrates a hydronic heater 100, according to certain embodiments. In general, hydronic heater 100 is a fuel burning appliance that heats HTF on demand and provides pumped circulation of the heated HTF for use in various portable or non-portable hydronic applications. Hydronic heater 100 itself may be portable and may serve as a central source of hot HTF for use with dependent heat exchangers such as fan coils for heating and drying of structures, multi-circuit line heat exchange hose or tubing for ground thawing, concrete curing, snow melting and slab heating, and custom hydronic heat exchange accessories and applications. In some embodiments, hydronic heater 100 may burn any appropriate fuel such as light diesel fuel, heating oil, natural gas, and propane gas in order to heat the HTF. In some embodiments, hydronic heater 100 may be ruggedly-designed for outdoor operation. In order to heat the HTF and provide it to other heating applications, hydronic heater 100 may utilize a combustion chamber such as combustion chamber assembly 200 of FIG. 2, which is discussed in more detail below.

FIG. 2 illustrates a combustion chamber assembly 200 of hydronic heater 100 of FIG. 1. In some embodiments, combustion chamber assembly 200 includes helically-coiled tubing 210 and a shroud 220. Helically-coiled tubing 210, which may include two layers of helically-looped tubes (e.g., inner coil assembly 310 and outer coil assembly 320), circulates HTF that is heated by combustion chamber assembly 200 and provided to an external heating application. As will be described in more detail below in reference to FIG. 3, a flame may be introduced into a first end 201 of combustion chamber assembly 200 towards a second end 202 of combustion chamber assembly 200 that is opposite first end 201. The flame causes hot flue gases to travel within the space enclosed by the inner coils of helically-coiled tubing 210 towards second end 202 where they are redirected back towards first end 201 for a second pass through helically-coiled tubing 210. On the second pass through helically-coiled tubing 210, some of the hot flue gas travels in a gap between the inner and outer coils of helically-coiled tubing 210, and some of the hot flue gas travels in a gap between the outer coils and shroud 220. Once the hot flue gasses reach the end of shroud 220 at location 225, they may escape helically-coiled tubing 210 via spaces between the outer coils and subsequently be vented out of combustion chamber assembly 200. The flow of flue gasses and the unique arrangement of helically-coiled tubing 210 and shroud 220 is described in more detail below in reference to FIG. 3.

Shroud 220, in general, is a cylindrical tube that encompasses a portion of helically-coiled tubing 210. In some embodiments, shroud 220 is made of stainless steel, but may be any other appropriate metal or material in other embodiments. Shroud 220 is generally shorter in length than helically-coiled tubing 210 as illustrated in order to permit hot flue gases 370 to radially exit helically-coiled tubing 210 after they have travelled back towards first end 201 (i.e., there is a gap starting at location 225). In general, the specific length of shroud 220 causes hot flue gasses to flow turbulently over the surfaces of both coils of helically-coiled tubing 210 most of the way back down the length of combustion chamber assembly 200 on its second pass. In some embodiments, shroud 220 is at least three-fourths the distance from second end 202 to first end 201, but may have any other appropriate lengths in other embodiments.

FIG. 3 illustrates a cut-away view of combustion chamber assembly 200 of FIG. 2, according to certain embodiments. Combustion chamber assembly 200 may include inner coil assembly 310, outer coil assembly 320, and refractory flue gas roller 340. Example embodiments of inner coil assembly 310 are illustrated and discussed below in reference to FIG. 6. Example embodiments of outer coil assembly 320 are illustrated and discussed below in reference to FIG. 7. Example embodiments of refractory flue gas roller 340 are illustrated and discussed below in reference to FIGS. 4A-4C.

In general, a burner 330 may introduce a flame 335 into first end 201 of combustion chamber assembly 200 as illustrated in FIG. 3. In some embodiments, flame 335 may be introduced horizontally into combustion chamber assembly 200 along a longitudinal axis (e.g., center axis 510) about which inner coil assembly 310 and outer coil assembly 320 are centered. Flame 335 may be contained within the center void of inner coil assembly 310 and generate hot flue gas 370 that travels towards second end 202 in the space enveloped by inner coil assembly 310. Hot flue gas 370 heats the HTF that is being circulated within inner coil assembly 310. Because the coils of inner coil assembly 310 are in tight mechanical contact with each other (e.g., the coils of inner coil assembly 310 may be welded together to form an air-tight cylinder), hot flue gases 370 are forced to travel to second end 202 before they are permitted to exit the inner coil chamber. To exit the inner coil chamber, hot flue gases 370 are divided and redirected by refractory flue gas roller 340 back towards first end 201. On the second pass, hot flue gas 370 is divided into two portions: first flue gas portion 372 and second flue gas portion 374. First flue gas portion 372 travels towards first end 201 in a first gap 382 that is between inner coil assembly 310 and outer coil assembly 320. Second flue gas portion 374 travels towards first end 201 in a second gap 384 that is between shroud 220 and outer coil assembly 320. Once first flue gas portion 372 and second flue gas portion 374 reaches the end of shroud 220 at location 225, they flow between spaces 380 in outer coil assembly 320 and into a sealed plenum 360. First flue gas portion 372 and second flue gas portion 374 then exit combustion chamber assembly 200 via a flue collar 350.

Inner coil assembly 310 is generally a helically-coiled tube of any appropriate size. Inner coil assembly 310 may have any appropriate overall length and diameter, but the diameter of inner coil assembly 310 is less than the diameter of outer coil assembly 320 so that inner coil assembly 310 may reside inside outer coil assembly 320 as illustrated. In such an arrangement, first gap 382 exists between inner coil assembly 310 and outer coil assembly 320. First gap 382 may be any appropriate distance, but in some embodiments is less than one inch. In addition, the length of inner coil assembly 310 (i.e., along a direction between first end 201 and second end 202) is greater than a length of shroud 220. Inner coil assembly 310 may have any number of coils. The coils of inner coil assembly 310 are generally in close contact with one another so as to prevent hot flue gas 370 from passing between the coils of inner coil assembly 310 and to provide a cylinder to direct hot flue gas 370 towards refractory flue gas roller 340. In some embodiments, each coil of inner coil assembly 310 is welded or otherwise coupled to adjacent coils. Particular embodiments of inner coil assembly 310 are discussed in more detail below in reference to FIG. 6.

Outer coil assembly 320 is generally a helically-coiled tube of any appropriate size. Outer coil assembly 320 may have any appropriate overall length and diameter, but the diameter of outer coil assembly 320 is greater than the diameter of inner coil assembly 310 so that outer coil assembly 320 may surround inner coil assembly 310 as illustrated. Furthermore, the diameter of outer coil assembly 320 is less than the diameter of shroud 220 so that shroud 220 may surround outer coil assembly 320 as illustrated. In such an arrangement, second gap 384 exists between outer coil assembly 320 and shroud 220. Second gap 384 may be any appropriate distance, but in some embodiments is approximately at least three-quarters of an inch, plus or minus ten percent. In addition, the length of outer coil assembly 320 (i.e., along a direction between first end 201 and second end 202) is greater than a length of shroud 220. Outer coil assembly 320 may have any number of coils. The coils of outer coil assembly 320 are separated from adjacent coils of outer coil assembly 320 by spaces 380 in order to allow first flue gas portion 372 to radially escape into sealed plenum 360 after travelling away from refractory flue gas roller 340 in first gap 382. Spaces 380 may be any appropriate distance and may be uniform or non-uniform along the length of outer coil assembly 320. In some embodiments, spaces 380 are approximately three-eighths of an inch, plus or minus ten percent, but may be other distances in other embodiments. Particular embodiments of outer coil assembly 320 are discussed in more detail below in reference to FIG. 7.

Both inner coil assembly 310 and outer coil assembly 320 circulate any appropriate HTF. In some embodiments, the HTF circulated by inner coil assembly 310 and outer coil assembly 320 is water. In other embodiments, the HTF is any other appropriate HTF such as glycol. In some embodiments, each of inner coil assembly 310 and outer coil assembly 320 has an inlet and an outlet (e.g., as illustrated in FIG. 5A) for circulating the HTF in and out of inner coil assembly 310 and outer coil assembly 320.

In some embodiments, the tubes of inner coil assembly 310 and outer coil assembly 320 are substantially equal in length (e.g., within 0-10%). By having tubes of substantially equal lengths, the flow of HTF within the tubes may be balanced. In some embodiments, spaces 380 between coils of outer coil assembly 320 help to equalize the lengths of the tubes of inner coil assembly 310 and outer coil assembly 320.

Refractory flue gas roller 340 is any appropriate redirection element for redirecting hot flue gas 370 that is travelling towards second end 202 back towards first end 201. In general, refractory flue gas roller 340 is contoured in a way that aids hot flue gas 370 to roll to the outside of the inner chamber and flow in the reverse direction on its second pass. In some embodiments, refractory flue gas roller 340 is solid metal (e.g., stainless steel or the like). In other embodiments, refractory flue gas roller 340 is not solid but instead includes an internal chamber for holding a portion of the HTF. Such embodiments may further increase the efficiency of combustion chamber assembly 200 by capturing additional heat from hot flue gas 370. Particular embodiments of refractory flue gas roller 340 are discussed below.

FIGS. 4A-4C illustrate various views of refractory flue gas roller 340 of combustion chamber assembly 200 of FIG. 2, according to certain embodiments. FIG. 4A is a top-down view of refractory flue gas roller 340, FIG. 4B is a side view of refractory flue gas roller 340 along line A-A of FIG. 4A, and FIG. 4C is a perspective view of refractory flue gas roller 340. As illustrated in these figures, refractory flue gas roller 340 may be generally circular in shape and may include a cone-shaped middle portion 410 and a rounded trench 420 around middle portion 410. Rounded trench 420 is generally operable to redirect hot flue gas 370 back towards first end 201 as illustrated in FIG. 3. In some embodiments, middle portion 410 may be centered on a longitudinal axis (e.g., center axis 510) on which inner coil assembly 310 and outer coil assembly 320 are aligned.

FIGS. 5A-5B illustrate various views of a coil assembly 500 of the combustion chamber assembly of FIG. 2, according to certain embodiments. Coil assembly 500 generally includes inner coil assembly 310 that is surrounded by outer coil assembly 320, as illustrated. In some embodiments, inner coil assembly 310 and outer coil assembly 320 (and thus coil assembly 500) are centered longitudinally on a center axis 510. That is, both inner coil assembly 310 and outer coil assembly 320 may be coaxial with respect to center axis 510. In general, center axis 510 runs from first end 201 towards second end 202.

FIG. 6 illustrates an example inner coil assembly 310 of coil assembly 500 of FIG. 5A. FIG. 6 illustrates how the coils of inner coil assembly 310 are in close contact with one another (e.g., they may be welded together) in order to prevent hot flue gas 370 from passing between the coils of inner coil assembly 310. In addition, the coils of inner coil assembly 310 may be welded or otherwise coupled to one or more support bars 610 at locations 620. Support bars 610 may be any appropriate material such as a metal. Any appropriate number of support bars 610 may be used by inner coil assembly 310.

FIG. 7 illustrates an example outer coil assembly 320 of coil assembly 500 of FIG. 5A, according to certain embodiments. FIG. 7 illustrates how the coils of outer coil assembly 320 are not in close contact with one another like the coils of inner coil assembly 310. Instead, the coils of outer coil assembly 320 have spaces 380 between adjacent coils that permits hot flue gas 370 to pass through outer coil assembly 320 and into sealed plenum 360. In some embodiments, a plurality of spacers 710 are coupled between the coils of outer coil assembly 320 in order to produce spaces 380. Spacers 710 may be welded or otherwise coupled between the coils of outer coil assembly 320 and may be made of any appropriate metal or other material. In addition, the coils of outer coil assembly 320 may be welded or otherwise coupled to one or more support bars 730 at locations 720. Support bars 730 may be any appropriate material such as a metal. Any appropriate number of support bars 730 may be used by outer coil assembly 320.

Although a particular implementation of combustion chamber assembly 200 is illustrated and primarily described, the present disclosure contemplates any suitable implementation of combustion chamber assembly 200, according to particular needs. Moreover, although various components of combustion chamber assembly 200 have been depicted as being located at particular positions, the present disclosure contemplates those components being positioned at any suitable location, according to particular needs.

Herein, “or” is inclusive and not exclusive, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A or B” means “A, B, or both,” unless expressly indicated otherwise or indicated otherwise by context. Moreover, “and” is both joint and several, unless expressly indicated otherwise or indicated otherwise by context. Therefore, herein, “A and B” means “A and B, jointly or severally,” unless expressly indicated otherwise or indicated otherwise by context.

The scope of this disclosure encompasses all changes, substitutions, variations, alterations, and modifications to the example embodiments described or illustrated herein that a person having ordinary skill in the art would comprehend. The scope of this disclosure is not limited to the example embodiments described or illustrated herein. Moreover, although this disclosure describes and illustrates respective embodiments herein as including particular components, elements, feature, functions, operations, or steps, any of these embodiments may include any combination or permutation of any of the components, elements, features, functions, operations, or steps described or illustrated anywhere herein that a person having ordinary skill in the art would comprehend. Furthermore, reference in the appended claims to an apparatus or system or a component of an apparatus or system being adapted to, arranged to, capable of, configured to, enabled to, operable to, or operative to perform a particular function encompasses that apparatus, system, component, whether or not it or that particular function is activated, turned on, or unlocked, as long as that apparatus, system, or component is so adapted, arranged, capable, configured, enabled, operable, or operative. Additionally, although this disclosure describes or illustrates particular embodiments as providing particular advantages, particular embodiments may provide none, some, or all of these advantages. 

What is claimed is:
 1. A system, comprising: a combustion chamber comprising a first end and a second end opposite the first end; a burner configured to introduce a flame into the first end of the combustion chamber, the flame generating a flue gas that flows from the flame towards the second end; a coil assembly within the combustion chamber, the coil assembly comprising: a first tube arranged into a plurality of inner coils, the plurality of inner coils contacting adjacent inner coils to prevent the flue gas from passing between the plurality of inner coils; and a second tube arranged into a plurality of outer coils that surround the plurality of inner coils, the plurality of outer coils being separated from adjacent outer coils by a plurality of spaces, wherein: the first and second tubes are configured to transport a heat transfer fluid (HTF); and the plurality of inner coils are separated from the plurality of outer coils by a first gap; a cylindrical shroud surrounding at least a portion of the coil assembly, the cylindrical shroud comprising a length that is less than a length of the coil assembly; and a flue gas roller configured to redirect the flue gas into a first flue gas portion and a second flue gas portion, the first flue gas portion flowing towards the first end of the combustion chamber in the first gap between the plurality of inner coils and the plurality of outer coils, the second flue gas portion flowing towards the first end of the combustion chamber in a second gap between the plurality of outer coils and the cylindrical shroud.
 2. The system of claim 1, wherein the plurality of inner coils and the plurality of outer coils are coaxial.
 3. The system of claim 1, wherein the plurality of inner coils and the plurality of outer coils are each welded to a plurality of support bars.
 4. The system of claim 1, wherein the first tube and the second tube comprise substantially equal lengths.
 5. The system of claim 1, wherein the flue gas roller is circular in shape.
 6. The system of claim 1, wherein the flue gas roller is solid metal.
 7. The system of claim 1, wherein the flue gas roller comprises an internal chamber for holding a portion of the HTF.
 8. The system of claim 1, further comprising a plurality of spacers welded between adjacent outer coils in order to provide the plurality of spaces between the plurality of outer coils.
 9. A combustion chamber, comprising: a first end and a second end opposite the first end; an inner helically-coiled tube comprising a plurality of inner coils, the plurality of inner coils contacting adjacent inner coils; and an outer helically-coiled tube comprising a plurality of outer coils that surround the plurality of inner coils, the plurality of outer coils being separated from adjacent outer coils by a plurality of spaces, wherein: the inner and outer helically-coiled tubes are configured to transport a heat transfer fluid (HTF); and the plurality of inner coils are separated from the plurality of outer coils by a first gap; a cylindrical shroud surrounding at least a portion of the outer helically-coiled tube; and a flue gas redirection element configured to redirect flue gas travelling towards the second end of the combustion chamber into a first flue gas portion and a second flue gas portion, the first flue gas portion flowing towards the first end of the combustion chamber in the first gap between the plurality of inner coils and the plurality of outer coils, the second flue gas portion flowing towards the first end of the combustion chamber in a second gap between the plurality of outer coils and the cylindrical shroud.
 10. The combustion chamber of claim 9, wherein the plurality of inner coils and the plurality of outer coils are coaxial.
 11. The combustion chamber of claim 9, wherein the plurality of inner coils and the plurality of outer coils are each welded to a plurality of support bars.
 12. The combustion chamber of claim 9, wherein the inner and outer helically-coiled tubes comprise substantially equal lengths.
 13. The combustion chamber of claim 9, wherein the flue gas redirection element is circular in shape.
 14. The combustion chamber of claim 9, wherein: the flue gas redirection element is solid metal; or the flue gas redirection element comprises an internal chamber for holding a portion of the HTF.
 15. The combustion chamber of claim 9, further comprising a plurality of spacers welded between adjacent outer coils in order to provide the plurality of spaces between the plurality of outer coils.
 16. A coil assembly for a combustion chamber, the coil assembly comprising: a first tube arranged into a plurality of inner coils, each inner coil contacting adjacent inner coils; a second tube arranged into a plurality of outer coils that surround the plurality of inner coils, the plurality of outer coils being separated from adjacent outer coils by a plurality of spaces, wherein: the first and second tubes are configured to transport a heat transfer fluid (HTF); and the plurality of inner coils are separated from the plurality of outer coils by a gap; and a cylindrical shroud surrounding at least a portion of the coil assembly, the cylindrical shroud comprising a length that is less than a length of the coil assembly.
 17. The coil assembly of claim 16, wherein the plurality of inner coils and the plurality of outer coils are coaxial.
 18. The coil assembly of claim 16, wherein the plurality of inner coils and the plurality of outer coils are each welded to a plurality of support bars.
 19. The coil assembly of claim 16, wherein the first tube and the second tube comprise substantially equal lengths.
 20. The coil assembly of claim 16, further comprising a plurality of spacers welded between adjacent outer coils in order to provide the plurality of spaces between the plurality of outer coils. 